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Study of gigantic third-order optical nonlinearity in low-dimensional correlated electron systems

低维相关电子系统中巨三阶光学非线性研究

基本信息

批准号：
13440090
负责人：
OKAMOTO Hiroshi
金额：
$ 7.74万
依托单位：
The University of Tokyo
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
2001
资助国家：
日本
起止时间：
2001 至 2003
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-13440090/
关键词：
Nonlinear optical effect Third order nonlinear susceptibility Strongly correlated electron systems Copper oxides Transition metal oxides Third harmonic generation 三次の非線形感受強相関係非線形光学定数

项目摘要

The purpose of this research project is to measure quantitatively third-order nonlinear susceptibility χ^<(3)> spectra and clarify the mechanism of third-order optical nonlinearity in one-dimensional (1D) correlated electron systems of halogen-bridged nickel compounds and 1D and 2D cuprates. We have performed several kinds of nonlinear spectroscopy measurements on these materials such as -scan measurements and transimission-and reflection-type third harmonic generation (THG) measurements. The main results are as followed.○ In the 1D cuprates and the nickel compounds, odd and even excited states are degenerate. In the 2D cupreates, on the other hand, the even excited state locates at the energy slightly lower than the odd excited state. Such a difference between the 1D and 2D cuprates is related to the fact that charge and spin degrees of freedom are separated in the 1D system, but coupled in the 2D system. In the 1D system, therefore, the transition dipole moments between the ground state and the odd excited state and between the odd and even excited states are enhanced and then the larger χ^<(3)> is obtained○The magnitude of χ^<(3)> of the bromine-bridged nickel compound evaluated by the reflection-type THG measurements is extremely large, exceeding 10^<-8> esu. In this compound, the relaxation of the photoexcited state is very fast, and the spectral width of the absorption is very small, suggesting its high potential as a good nonlinear optical material for applications.

本研究的目的是定量测量卤素桥联镍化合物和一维、二维铜酸盐一维关联电子体系的三阶非线性极化率χ^<3>谱，阐明三阶非线性光学效应的机理。我们对这些材料进行了几种非线性光谱测量，如扫描测量和透射和反射型三次谐波产生（THG）测量。主要结果如下：○在一维铜酸盐和镍化合物中，奇、偶激发态是简并的。另一方面，在二维铜酸盐中，偶激发态位于比奇激发态稍低的能量处。1D和2D铜氧化物之间的这种差异与电荷和自旋自由度在1D系统中分离，但在2D系统中耦合的事实有关。因此，在1D系统中，基态和奇数激发态之间以及奇数激发态和偶数激发态之间的跃迁偶极矩增强，然后获得较大的χ 2 <（3）>。通过反射型THG测量评估的溴桥连镍化合物的χ 2 <（3）>的幅度非常大，超过10 μ <-8>esu。在这种化合物中，光激发态的弛豫非常快，并且吸收的光谱宽度非常小，这表明其作为良好的非线性光学材料的应用的高潜力。